Model output discussion - deep cold inbound?

[feb1991blizzard]

9 minutes ago, Scorcher said:

Is this because the GFS isn't showing you what you want to see? The evolution looks very feasible to me. That low approaching from the west is always going to cut off the supply of cold air sooner rather than later. The Atlantic just looks far too active to me to sustain a cold easterly flow for any more than a few days.

Normally i would agree with you about the hopecasting and think its a myth that breakdowns 'always' get put back and when i see a graph where a large cluster of ensembles shoot up in temperature even if it is in FI and from memory when you're coming out of a cold spell they very rarely flip back - 2012 being a case in point and if i had gone with my own instincts would have saw it coming before anyone else, including some highly qualified pro's, however, this is different a little, the lows seem to be forever sliding south lately as soon as they hit 168, plus also when judging the Atlantic's ferocity, always look for which way lows are tilted and how fast they are moving, don't just look at individual frames, run the sequence through on meteociel, so although i think expecting the next few of them next week to all be channel lows feeding a continual beast would be a bit of a leap of faith, i can't see them getting much further North than the Midlands either, perhaps Shropshire, Stafford and Crewe getting a pasting.

[Don]

31 minutes ago, sheikhy said:

Another thing to note is the ukmo and ecm have a bit more amplification around eastern states at 144 hours which helps disrupt the trough a bit more!!the gfs is much flatter for the same time period!!

My main concern is the latest Metoffice weekend forecast which is showing potential rain for the far southeast for Sunday, so it doesn't look like they're discounting the GFS12z scenario ATM?

[Polar Maritime]

Folk need to stop over analysing snow charts it's far far to early to be giving them any credit whatever at this range. In these set-ups snow probabilitys can change in just a few hours given the very unstable Easterly flow incoming...

Edited February 4, 2021 by Polar Maritime

[tight isobar]

Just now, Don said:

My main concern is the latest Metoffice weekend forecast which is showing potential rain for the far southeast for Sunday, so it doesn't look like they're discounting the GFS12z scenario ATM?

Last one in this .. then the models.. those graphics will raise n drop as each run b4 engagement... we’ll leave this now aye....

[sunnijim]

7 minutes ago, Weather vane said:

Apologies for the ignorance. but I often see reference to Exeter. Is that where the met office is based? And if so, where can you get the Exeter 'comments' ?

Long range forecast

WWW.METOFFICE.GOV.UK

---

Our long range forecast (which is updated on a daily basis) provides an indication of how the weather might change, or be different from normal across the whole UK.

 

[sheikhy]

Just now, Don said:

My main concern is the latest Metoffice weekend forecast which is showing potential rain for the far southeast for Sunday, so it doesn't look like they're discounting the GFS12z scenario ATM?

Cannot discount the gfs scenario what so ever!!its been just as resolute as the other in regards to that low on sunday!!ecm is about to come out in 15 mins and we will get a better idea hopefully!!the 06z was very similar to the gfs for sunday!!

[Guest]

According to CFSV2...The cold coming this weekend is just an Aperitif!

 

Edited February 4, 2021 by Guest

[chris55]

GFS 12z ensembles once again show lots of scatter (i'm talking 7th-11th.) If the Operational had gone towards the cold side rather than the milder side the posts in the forum would be more positive in terms of cold prospects continuing, however because the clustering is spread, confidence in either outcome would be the same.

GFS suite looks to be edging in too much less cold air into the south east quadrant and this is making the LONDON ensembles skew the overall picture.

 

[Don]

4 minutes ago, sheikhy said:

Cannot discount the gfs scenario what so ever!!its been just as resolute as the other in regards to that low on sunday!!ecm is about to come out in 15 mins and we will get a better idea hopefully!!the 06z was very similar to the gfs for sunday!!

True, but I suppose my main concern with the GFS is what it does later in the run!

Edited February 4, 2021 by Don

[TSNWK]

11 minutes ago, tight isobar said:

Points of note via the raws: 1 concentrate on Saturday >Tuesday!   2: assume everything beyond them time params are pie in the sky. : 3 dissmiss all precipitation data charts until 24hrs out of notions. 4: expect a rollercoaster ride until saturdays 12z suites. 5 ; and the most important..let the flow@easterly incursion actually be Door  knocking b4 looking for possible routes of breakdown,to herald the return of bk to basics... take these into consideration ... and you’ll save yaself pulpatations and unnecessary greif!!!

When ever  new thread is created we usually have a introduction blurb - can we have this for the next thread please Mods?

[sheikhy]

Yeh dont think am too concerned with what ecm shows before 144 hours but more thereafter!!we need that disruption to continue in the atlantic from the 00z!!

Edited February 4, 2021 by sheikhy

[Anthony Burden]

GFS with different Synoptics on tracking of Atlantic lows and keen to raise temperatures

with the Atlantic taking command and northern blocking collapsing.GEM ICON UKMO 

all keeping the U.K. in the cold air to the end of their runs except possibly the very far south coast.

A long cold very cold spell looks on the cards.

[KTtom]

Quick question, ive noted GEM always has colder 850 temps compared to the gfs...is this factored into verification stats...and any ideas why?

Edited February 4, 2021 by KTtom

[Weather vane]

8 minutes ago, sunnijim said:

Long range forecast

WWW.METOFFICE.GOV.UK

---

Our long range forecast (which is updated on a daily basis) provides an indication of how the weather might change, or be different from normal across the whole UK.

 

Ha, ha, I read those nearly every day; the mythical 'Exeter' now uncloaked (for me !)

[tight isobar]

4 minutes ago, KTtom said:

Quick question, ive noted GEM always ha scolder 850 temps compared to the gfs...is this factored into verification stats...and any ideas why?

The model diagnosis -prognosis and overall performance are evaluated @500 geopotential height....edit; perhaps another valid reason to take 850 hpas as a guide.. not a promise... as some do

Edited February 4, 2021 by tight isobar

[Paul_1978]

1 hour ago, nick sussex said:

The GFS to be blunt is a bit of a shocker and rapidly goes downhill as it allows the PV in Canada to phase with Atlantic shortwave energy , this then feeds energy into that and you see the pattern becomes more progressive .

 I hate to use the word shocker when there will still be some snow but really not a good run in terms of extending the cold .

 

49 minutes ago, Keefo said:

GFS 12z only one run. There will be no doubt subtle changes in either direction between now and the weekend. Keeping us all occupied though!!!

To be fair though, the GFS has pretty much consistently shown the end of the cold-snap-that-hasn’t-started-yet next Thursday for a few runs now. There was a hint on the 0z of the low not being so deep and perhaps elongating and sliding under the block. 

So it’s not one run or any more of a shocker than it was yesterday at the same time. 

However as we all know the GFS has a tendency to overblow lows in the Atlantic and they often weaken as the timeframe gets closer, and if that happens I don’t fancy it pushing the cold away as easily. 

Intriguing ECM coming up!

[DAVE_ALLEN]

46 minutes ago, kold weather said:

UKMO has big time upgraded the snow threat on Sunday, looks similar to the GFS but no warm sector to speak of over the SE:

5-10cms across the SE, 15cms N.Kent and Suffolk.

@nick sussex that run is about the worst possible way to evolve out of the pattern. If its going to go like that, may as well have that first low further north so we can get snow out of that!

Maybe its me... but that has mm, Kold.. Not cm ??

[CentralSouthernSnow]

3 minutes ago, Paul_1978 said:

 

To be fair though, the GFS has pretty much consistently shown the end of the cold-snap-that-hasn’t-started-yet next Thursday for a few runs now. There was a hint on the 0z of the low not being so deep and perhaps elongating and sliding under the block. 

So it’s not one run or any more of a shocker than it was yesterday at the same time. 

However as we all know the GFS has a tendency to overblow lows in the Atlantic and they often weaken as the timeframe gets closer, and if that happens I don’t fancy it pushing the cold away as easily. 

Intriguing ECM coming up!

Well it’s 4 models at the moment Vs Gfs 12 for the low next week. I personally think it will track south. Let’s see what ECM says! 

[chris55]

Im hoping for an Atlantic undercut at day 6-7 on ECM.... With a southern blizzard ensuing that dumps lots of snow, but simultaneously draws in -15 850s to the east just to keep everyone as happy as possible..... we can but dream

T24 and we are off....

Edited February 4, 2021 by chris55

[Man With Beard]

19 minutes ago, Don said:

My main concern is the latest Metoffice weekend forecast which is showing potential rain for the far southeast for Sunday, so it doesn't look like they're discounting the GFS12z scenario ATM?

To be fair a number of models have skirted with sleety spells in the very far SE, such as ARPEGE. I cannot imagine with the uppers forecast that anywhere except maybe Deal / Margate / Dover will be in that situation for too long, and it must be fairly likely the whole of the country will be in snow-friendly conditions for most or all of the Sunday to Wednesday period.

[Yarmy]

2 minutes ago, DAVE_ALLEN said:

Maybe its me... but that has mm, Kold.. Not cm ??

1mm precipitation = 1cm snow (approximately)

[kold weather]

Just now, DAVE_ALLEN said:

Maybe its me... but that has mm, Kold.. Not cm ??

Your correct, but remember thats a 6hrs snapshot, theres plenty either side believe me. Also remember, we probably have a ratio around 8:1, maybe a touch higher? So 1mm equals probably 0.8cms.

The snow depth is between 5-10cms for the even, with a small region of 15cms for .Kent and Suffolk. Take a look at weather.us, it has the run on there.

 

[kold weather]

25 minutes ago, Don said:

My main concern is the latest Metoffice weekend forecast which is showing potential rain for the far southeast for Sunday, so it doesn't look like they're discounting the GFS12z scenario ATM?

I posted this in the SE thread, but out of 82 seperate operational and ensemble members that weren't GFS/ensembles that I looked at earlier today on the 00z suite, only 7 were as warm as the GFS run is for the far SE.

The odds are very low, and 4 out of those 7 were GEM - of which the 12z GEM is now only 3 runs...

Not impossible mind you, but I think its probably more chance of it being too far east as a percentage on the overall suite.

Edited February 4, 2021 by kold weather

[sheikhy]

Ecm not as deep with the low at 48 hours in france like gfs!!will it make a difference?!!

[Cloud 10]

11 minutes ago, KTtom said:

Quick question, ive noted GEM always has colder 850 temps compared to the gfs...is this factored into verification stats...and any ideas why?

 

The GEM had a problem under-estimating 850's a few years ago which was supposedly fixed,but it still appears to be struggling in that department.